


Present

by Omoni



Series: Random Undertale Stories and Drabbles [9]
Category: Undertale (Video Game)
Genre: Alphynecentric, Alphys/Undyne-centric, Birthday Sex, Established Alphys/Undyne, F/F, Fluff, Fluffy Smut, Gay Sex, Lewd Fluff, Lewff, Spoilers - Undertale Pacifist Route
Language: English
Status: Completed
Published: 2016-10-26
Updated: 2016-10-26
Packaged: 2018-08-27 06:09:27
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,413
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8390233
Author URL: https://archiveofourown.org/users/Omoni/pseuds/Omoni
Summary: It's Undyne's birthday, and Alphys has a plan to make it start extra-special.





	

**Author's Note:**

  * For [the_fox333](https://archiveofourown.org/users/the_fox333/gifts).



> HAPPY BIRTHDAY, THE_FOX333!!! ;3

Alphys woke up, as usual, before Undyne, but on this day, it was actually intentional. With a devious grin, Alphys slipped out of bed as quietly as possible, for once not waking Undyne as she usually did. Luckily for her, Undyne had spent the night celebrating her upcoming birthday with Papyrus, and it had gone late. Therefore, Undyne barely stirred when she left the bed. Alphys grinned wider, snuck to the bathroom, and freshened up a bit, before tiptoeing back, slipping off her nightgown and underwear, and sliding back into bed under the covers.

She paused, making sure Undyne was still asleep, which she was. Slowly, she scooched herself closer, and slipped her arms around Undyne's slim waist, shifting her body right up against her back as well as pulling Undyne to her. Immediately, Undyne inhaled sharply and pushed back against her, her hands reaching down and covering Alphys's. Her eye didn't open, though she did smile. She could clearly feel that Alphys was naked behind her, and was quite pleased about it, too. 

"Good morning, Undyne," Alphys murmured against her shoulder, kissing her there gently. "Happy birthday."

"Mm," Undyne replied. "Morning, nerd. Thank you."

"So, today, I-I've made lots of plans," Alphys continued, nuzzling Undyne's neck slowly as she spoke. "But your f-first present is already here. And... it's already unwrapped."

Undyne chuckled softly, moving to turn around, but Alphys stopped her. Instead, she slipped one hand down Undyne's stomach, gently tracing the flat muscle and soft, scarred skin, her touch very light, and Undyne sighed again and shivered, relaxing and keeping her hand over Alphys's, going further and pushing her hand lower. 

Alphys moved closer, gently kissing the curve of Undyne's neck. Undyne's legs moved back and tangled with hers a little, making her smile a little, especially when she felt gooseflesh rise up along her skin. Alphys moved her other hand over one of her breasts, which only increased that - as well as her smile. 

When Alphys's hand reached between Undyne's legs, Undyne shifted and spread them a little, pulling her hand down closer and sending a jab of heat into Alphys without control. Undyne had that affect on her, after all, especially like this. Carefully, she curved her fingers up and dragged them over Undyne's folds slowly, feeling that she was already wet and warm. Undyne made a soft noise at that, shifting herself backwards as well as pulling Alphys's hand closer. Alphys moved her fingertips up and trailed them over her clit slowly, now licking along the curve of Undyne's neck slowly. Undyne moaned softly, and that only encouraged Alphys further. 

Alphys moved her fingers along Undyne's clit slowly, finding ease with how wet she was becoming the more she stroked, and soon Undyne was moving along with her, holding onto Alphys's forearm with one of her own hands hard, the other digging into the mattress below her. Her eye was closed, and with each stroke, her face was getting redder and redder, her breaths short. Alphys nipped her neck gently, and she gasped and arched back against her, her nails digging into her arm. "Alphy..." she growled out, and in reply, Alphys bit her again and increased the pace of her fingers, using two along her clit, now. 

Soon, Undyne was crying out with every other breath, her body so warm that Alphys could feel it against her own. She moved her lips up to Undyne's ear and gently ran the tip of her tongue over the sensitive membrane, and again Undyne said her name, the sound strained and desperate, her hand clutching her arm hard and trying to urge her to move faster. "Please, Alphy," she whispered, her voice strained. "Please, _please, Alphy..."_

Alphys curved her fingers and pressed down a little harder, increasing their pace, and Undyne groaned out, _"Yes,"_ her voice breaking into another long moan. Alphys pushed closer and buried her face into Undyne's shoulder as she felt Undyne's body stiffen and heard her cries drag out as she came, squirming a little as it went through her body. 

Alphys slowed her hand, then pulled it away, as Undyne calmed, moving to hold her close as she caught her breath. Undyne moved away to turn around and face her, grabbing hold of her and pulling her close, still shaking a little from release. "Good?" Alphys wondered softly, stroking her hair.

"Mmhm," Undyne agreed, her face buried in her chest. "Excellent." 

Then, to Alphys's surprise, her hands moved down Alphys's back and cupped around her rear, making her squeak. When she looked down at Undyne, she was grinning deviously. "More," she murmured, sending a wave of heat through Alphys. Then, she felt Undyne's tongue lick along one of her nipples, and she leaned back, her eyes closing and her hands reaching for her. Undyne easily leaned on her, then moved on top of her, shifting to lick her other breast slowly.

"Wait, it's _your_ birthday!" Alphys protested, especially when Undyne's hand reached down over her stomach and between her legs. "I should be the one on top, for you, Undyne!"

"Nope," Undyne replied simply, moving her head up and kissing her, instead, both to silence her as well as to keep going. Alphys immediately was hers and forgot why she was protesting, especially when she felt Undyne's tongue slip between her lips and meet hers. Alphys clung to her, her arms going around Undyne's neck and her hands going into her hair, her tail wrapping around one of her legs tight. Undyne chuckled softly against her lips, pressing down onto her and shifting her legs apart, moving hers in the opposite way. Alphys made soft sound, licking Undyne's tongue and pulling her closer.

Undyne finally shifted close enough for them to touch, and found that Alphys was almost as slick as she was, turning her on even more. Alphys moaned softly against her lips, her eyes still shut, and Undyne pushed down closer in order to get better friction between the two of them, and this time it was Undyne who was moaning, feeling that sweet contact intensify and loving it. Alphys tugged on her hair a little, then pulled away a little to apologise breathlessly, but Undyne simply shifted her hips and rubbed closer, catching her into another deep kiss. Alphys pushed up against her in return, crying out softly.

For a wonderful moment, one that lasted quite a bit, they moved slow together, feeling the slow build of pleasure between them and wanting to make it last - Alphys especially thinking of Undyne. She pulled away for a moment to slip her hands to Undyne's face and look right into her eye, despite barely able to keep her breath steady. Undyne grinned down at her, her eye practically glowing, and she couldn't resist her anymore - again they kissed, and hard, this time. 

With that, Undyne started to increase the pace, truly unable to hold back anymore, either. Alphys cried out again, the sound muffled, but she met her pace and even increased it, her body and her blood flashing hot. She pulled from the kiss to cry out again, arching back beneath Undyne and holding her close, before her hands went to her shoulders, her claws digging in, and her moves became sporadic and uncontrolled. Undyne pulled her close and kept moving, and Alphys keened out her name, her claws leaving marks, as she came. Undyne held her close as she eased through it, whimpering breathlessly and panting to catch her breath, her hot face buried into Undyne's shoulder.

Once she caught her breath, Undyne grinned again and began to move once more, only still in that frenzied pace. Alphys groaned out, her head going back again and her eyes shutting tight, and Undyne watched her, loving to watch her, finding her own pleasure building just from the sight of hers alone, let alone the pace she set herself. 

Soon, though, she felt her own stamina crumble, and she shut her eye, gritting her teeth and pushing down against Alphys hard as she was rocked by her second orgasm, unable to suppress a long growl from how wonderful it felt. Alphys pulled her down and held her close, still breathing hard, and Undyne collapsed, now as breathless as she.

"Hah..." Alphys breathed out after a moment, her eyes still closed. "Happy... b-birth... day...?"

"Mm," Undyne replied, smiling and burying her face between Alphys's breasts gently, causing her to giggle tiredly. "Very much so."


End file.
